Multiphysics co-simulation: definitions


Generally, the term coupling is used when we wish to study, for a given device, several physical phenomena: electrical, magnetic, thermal, mechanical...

Each phenomenon is described by an equation (equations of Maxwell, equation of Fourier, circuit equation, mechanical equation...). Therefore, the coupling requires that a more complex system of equations be solved.

Strong / weak coupling: definitions

In general we speak about:

  • a strong coupling: when a simultaneous solving process of two systems of equations is carried out (example: in case of the field-circuit coupling, the equations of the magnetic field and the circuit equations are solved simultaneously)

  • a weak coupling: when the two systems of equations are solved independently , which imposes the data transfer from one system to another (example: in case of the kinematic coupling, the equations of the magnetic field and the mechanics equations are successively solved for each time step).

A strong coupling can be carried out only internally (within the software). A weak coupling can be realized internally (within the software) or in association (combination) with other software items.

Couplings proposed in Flux

The couplings proposed in Flux are the following:

  • circuit coupling (strong coupling)
  • kinematic coupling (weak coupling)

These couplings are entirely incorporated and available in the form of Flux modules (functionalities proposed by the software).


In order to carry out the coupling with other items of software, new functionalities allowing the external data exchange.

We speak about multiphysics co-simulation.


Examples of software items which can be coupled with Flux:

  • FLUENT: software of numerical simulation of fluids flows (Computational Fluid Dynamics: CFD)
  • EMTP: software of simulation of transient electromagnetic phenomenon in the electrical networks.
  • MpCCI: software for the coupling of various simulation codes
  • Flux: for instance Magneto-Thermal co-simulation